AT&T said on its earnings call today that it activated 400,000 to 500,000 3G iPads during Q2.

Remember that was basically just the last two months of Q2, as the iPad 3G didn't ship until the end of April.

It's hard to tell what that means for the iPad 3G vs. wi-fi-only mix, because AT&T only operates in the U.S., but it sounds pretty good. Apple shipped 3.27 million iPads overall last quarter, but into several countries.

It's "surprising" how many business customers are approaching AT&T about the iPad. Whereas business customers were famously skeptical and reluctant about the iPhone at first -- and have since warmed up to it -- they are apparently very eager about the iPad. AT&T said a lot of companies have iPad trials going on, and many see opportunities to use the iPad in their business as a laptop replacement. Look out, Microsoft!

iPad users are using more data per month than the typical iPhone customer, but less than the typical laptop-card customer, which makes sense.

75% to 80% of the iPad 3G subscribers are at the more expensive ($25/month) AT&T 3G data plan. Overall monthly bills in the $25-$30 range, including early customers who signed up for the $30/month unlimited plan before it was discontinued.